TPS759: TPS75925

Hi Nasrin,

5V -> 2.5V @ 4-5A is a lot of power dissipation [PD = (5-2.5) * 4 = 10W)]. If you want to use an LDO for this 2.5V supply you will need to get the input voltage down, otherwise it will just cycle in and out of current limit and will not be functional. The max dropout voltage spec for this device is 750mV across temperature, so have you considered using a buck converter to more efficiently get the 5V down somewhere closer to 3.3V?

Regards,

Nick

Hi Nick, 

Thanks for you reply. 

Do you suggest to use Buck to bring down 5V to 3.3V , then use TPSTPS75925 to 2.5V?

Do you have any other recommendation, I have limited space.

Is there any Buck 5V to 2.5V and can handle 6-7 A output current?

Hi Nasrin,

Yes that is what I was suggesting. With this level of output current you will either need to minimize the headroom for an LDO or use a buck regulator to more efficiently get the voltage down. I'm going to assign this post to the buck regulator team to help find a part that can do this.

Regards,

Nick

TPS759xx: With Power Good Fast-Transient Response 7.5-A Low Dropout Voltage Regs datasheet (Rev. E) (ti.com)

I'm just confirming with you the part number again TPS75925KTTT.

in the datasheet says only 400mA dropout at 7.5A and the max current is 7.5A. it's interesting why it will be in current limit situation when I'm just drawing 4 A.

Hi Nasrin,

It will not be in current limit, it will be in thermal shutdown mode. The thermal resistance for the KTT package is 38.7C/W, and with 10W power dissipation that is a junction temperature rise of 387C, much higher than the thermal shutdown temperature. If you were to get the input voltage down to 3.3V, the power dissipation (using the same numbers as above) would only be (3.3V - 2.5V) * 4A  = 3.2W, and this would correspond to a junction temperature rise of 38.7C/W * 3.2W = 124C. Adding the ambient temperature to this is still over the recommended operating conditions junction temperature of 125C, but with a good layout with thermal performance in mind you can also improve the thermal metrics and you could get that thermal resistance down. It would not be possible to get the thermal resistance in the 10W case down enough for it to be feasible. 

Regards,

Nick

Hi Nasrin,

The TPSM82866A is a very small, efficient buck power module that can do 5Vin to 2.5Vout at 6A.  Does it work for you?

Thanks,

Chris

This should work. But the part is out of stock.... any other similar option and available to purchase

Yes, this is a difficult market to find parts these days.  When do you plan to go to production and what volumes do you plan on needing?  How much output current do you need?  

If you have a TI sales contact, they can possibly get you a few units soon or you can order EVMs to evaluate the device.  This would allow you to choose the best device in the long run, rather than limiting yourself to what happens to be available this week or next.  On the other hand, if you plan to go to production soon, then you need something available now in sufficient quantities.

Chris

Yes! I’m planning for production in 3-4 weeks.

I need quantity of. 20-30.

input voltage 5V, output 2.5V and output current between 6-7A should work. Do you have any options available?

Oh, wow.  That's soon.

Here is our parametric search for finding a buck power module, which will be the easiest device to design in such a short time: https://www.ti.com/power-management/non-isolated-dc-dc-switching-regulators/step-down-buck/buck-modules-integrated-inductor/overview.html

Using your requirements and stock requirements, PTV05010W and PTH04T241W look good.  Would these work for you?

Chris